SUMMARY

1. In this study, the effects of nutrient (N and P) deficiency and the importance of essential polyunsaturated fatty acids (PUFA) [eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA)] to tropical cladocerans, growth and reproduction were determined in a growth bioassay. 2. The animals were fed N ⁄P-sufficient, N-deficient and P-deficient algae, and also N and P-deficient algae supplemented with fish oil emulsions rich in EPA and DHA. 3. Cladocerans showed different responses to nutrient-deficient algae and also to supplements of fish oil emulsions. Moina micrura was most sensitive to P-deficient alga and, surprisingly, grew better and produced more eggs in N-deficient alga than in N ⁄P sufficient alga. Ceriodaphnia cornuta was less sensitive, growing well in both N and P-deficient algae. This species, however, had a lower clutch size in N-deficient alga. On the other hand, Daphnia gessneri was the most sensitive to mineral limitation, showing decreased growth and clutch size in both nutrient-deficient algae. 4. The PUFA supplements to nutrient-deficient algae increased growth rates only for M. micrura and C. cornuta, suggesting that these fatty acids are important food requirements for these species